The present invention relates a method of producing water-insolubilized regenerated collagen fiber, and more particularly, to a method of producing water-insolubilized regenerated collagen fiber, which can substantially maintain the color and the high knot tenacity inherent in the collagen and which also maintains chemically modifiable carboxyl groups of the collagen as it is without being chemically modified.
Among the protein fibers, the regenerated collagen fiber exhibits a high mechanical strength like silk, and, thus, is used in various fields. Particularly, the regenerated collagen fiber is a protein fiber maintaining a characteristic molecular structure derived from collagen and, thus, is close in drape, luster and feel to the human hair that is a natural protein fiber having complex fine structure. Such being the situation, it is attempted to use the regenerated collagen fiber as an animal hair-like fiber such as a fur, or the hair.
In general, the skin or bone of an animal is used as a raw material of the regenerated collagen. The regenerated collagen can be produced by treating these raw materials with an alkali or an enzyme to obtain a water-soluble collagen, followed by extruding and spinning the water-soluble collagen in an aqueous solution of an inorganic salt. Since the regenerated collagen fiber thus obtained is soluble in water, some treatments are applied in order to impart resistance to water to the collagen fiber. As a method for making the regenerated collagen fiber insoluble in water, it is known to the art to treat the water-soluble collagen fiber with an aldehyde compound such as formaldehyde or glutaric aldehyde. It is also known to treat the regenerated collagen fiber with metal salts such as various chromium salts, aluminium salts or zirconium salts to make the regenerated collagen fiber insoluble in water. In the case of using an aldehyde compound other than formaldehyde or a chromium salt, the resultant fiber is colored, resulting in limitation in the use of the treated collagen fiber for manufacturing hairs of various colors such as a white hair or a golden hair. In the case of using formaldehyde, it is certainly possible to obtain a colorless fiber. However, the treated fiber is not satisfactory in beauty.
A colorless treating method of a regenerated collagen fiber using an epoxy compound is proposed in Japanese Patent Disclosure (Kokai) No. 4-352804. In the case of using glycidyl ether of polyhydric alcohol that is described in this prior art as a particularly desirable compound, it is certainly possible to achieve a colorless treatment. However, the knot tenacity is lowered, with the result that a problem tends to be generated during manufacture of the hair decorative article such as the filling step or a sewing step included in the manufacturing process. Also, a colorless treatment can be achieved by some of the methods using the metal salts noted above. However, since the carboxyl groups, the reactive groups, in the collagen are sequestered by the metal salt, the carboxyl groups fail to be chemically modified further. As a result, it is impossible to impart a new function such as a permanent wave to the regenerated collagen fiber after the treatment.